Previous residential or enterprise cellular access devices have tended to be one of two types:                Cellular retransmitter/booster, and        Femtocell        
In a Cellular retransmitter, the RF signal from the cellular handset is received at the repeater, where it is boosted and typically relayed to the Cellular Operator (CellOp) tower using a more powerful antenna. This provides in-house cellular coverage in areas where the signal indoors would otherwise be weak. The cellular handset does not register with the repeater—it is operating purely by amplifying the RF signal.
In a femtocell, the cellular handset registers with the femtocell as it would with a base-station in a cellular network. The femtocell then encapsulates data and signaling exchanged with the handset into IP packets, and transmits to the CellOp using the Internet. All calls established using the femtocell are routed over the CellOp's network, and the femtocell is remotely managed by the CellOp.
While both approaches offer a high-quality cellular signal within the building, they both suffer from the following disadvantages:                Calls can only be established or received using the CellOp network that the cellular handset is registered with,        In the case of the repeater, no additional services can be offered to the user,        In the case of the femtocell, the cellular handset is effectively connected to the CellOp's network (albeit over an IP backhaul), and the femtocell is only associated with a single CellOp,        Neither approach allows calls to be placed from the standard cellular handset using an Internet Protocol Service Provider (IPSP) for improved quality or toll avoidance, and        Neither approach allows the user of the cellular handset to gain access to other next generation IP-based services such as Presence, Instant Messaging or using other services such as those offered by IPSPs (e.g. Yahoo!, Skype or Google).        
The present industry trend is to address some the above disadvantages via a multi-service handset, e.g. a handset capable of handling cellar and voice over IP (VOIP) calls.